Researchers from health institutions in Taiwan and California recently conducted a study, published in JAMA Neurology, to determine the association between low-dose aspirin and bleeding in the skull.

To do so, they examined 13 previous studies that observed more than 130,000 adults, aged 42 to 74. The subjects, who did not have a history of heart attack or stroke, were prescribed low-dose aspirin of 75 to 100 milligrams or a placebo to prevent these conditions.

After analyzing the results, they found those who took the placebo had a 0.46% risk of head bleeding. Those on the low-dose aspiring had a 0.63% risk, which was the equivalent of 2 out of every 1,000 people.

The authors noted those of Asian backgrounds and those with a body mass index under 25 had the greatest risk.

“The absolute magnitude of these adverse effects is modest, but clinically relevant,” study co-author Wen-Yi Huang said in a statement. “Given that the many individuals in the general population have a very low risk of atherosclerotic cardiovascular events, if low-dose aspirin is given universally, adverse outcomes from intracranial hemorrhage may outweigh the beneficial effects of low-dose aspirin.”

In March, new guidelines from the American Heart Association (AHA) recommended most older adults should no longer take a low-dose aspirin every day to prevent a heart attack or stroke.